不同分子量的腐殖酸存在下2种无机砷的生物毒性效应研究

水环境中天然有机质会与砷形成络合物,进而影响砷的迁移、转化和生物毒性。研究利用超滤方法将腐殖酸(humic acid, HA)分为5个不同分子量的组分,以大型溞为受试生物,探究了不同分子量HA存在下砷对大型溞的毒性效应。结果表明,不同分子量的HA均缓解了As(Ⅲ)和As(Ⅴ)对大型溞的氧化应激损伤和细胞膜损伤,并降低了砷对MT的诱导量。其中1～30 k Da的HA对砷的缓解效果最好,1 k Da的HA毒性缓解效果最差,可能的原因是HA与砷的络合增加溶液中络合态砷的含量,而络合态砷难以进入细胞并被生物利用。不同分子量的HA对砷毒性的缓解差异与其跟砷的络合比例不同有关。

Arsenite and Arsenate Toxicity to Daphnia magna on the Coexistence of Humic Acid with Different Molecular Weights

Natural organic matter (DOM) may affect the migration, transformation and bioavailability of arsenic in aquatic environment by forming As-DOM complex. Using Daphnia magna as the case, humic acid (HA) was divided into 5 groups by ultrafiltration to determine the impacts from different molecular weights on arsenic toxicity in aquatic environment. The results indicated that all HA fractions can significantly alleviate the oxidative stress and membrane damage induced by As, and in the meanwhile reduce MT concentration. In particular, HA from 1-30 kDa fraction had the most remarkable alleviation effect, while the alleviation effect of HA (<1 kDa) was the lowest. The possible reason is that the complexation of HA with arsenic could increase As-DOM concentration in exposed medium, which is difficult to enter cells and be assimilated by organism. The effects of HA in alleviating arsenic toxicity with different molecular weights were related to complexation ratios.